超声速流中激波/湍流附面层干扰数值模拟

采用修正的B／L湍流模型以及多块结构化网格求解了二维N-S方程。分别对超声速流和高超声速流中的激波／湍流附面层干扰进行了数值研究。本文首先研究了进口马赫数为2．96的超声速流。计算结果准确预测了入射斜激波在平直壁面引起湍流附面层分离的流动特征：分离点的反射激波、分离包引起的膨胀扇以及再附点的反射激波。计算的壁面压力分布与实验值吻合较好，计算的分离区长度与实验值比较有一定误差。本文还对进口马赫数为9．22的高超声速流中压缩角引起的激波／湍流附面层干扰进行了数值研究。计算结果与实验结果吻合较好。     

激波过弯道绕双圆柱流场

采用单曝光光栅干涉或双曝光光栅干涉，研究激波过弯道绕双圆柱传播的微波流场。采用单曝光法，成功显示入射激波到第一圆柱上的反射、绕射，到达第二圆柱上的反射、绕射。在同一底片上采用双次曝光，第一次脉冲记录直道上的平面波，第二次脉冲记录激渡过弯道绕双圆柱流场。这些照片对于研究反射、绕射及它们边界的相互作用是很有用的。     

考虑高载和阻尼介质时刚塑性圆板的塑性动力分析

本文研究了阻尼介质对刚塑性圆板在高载(冲击荷载)作用下塑性动力响应的影响,得到了解析解并对此解进行了讨论。当阻尼介质参数趋于零时,本文结果与无阻尼解一致。文中还画出了荷载与阻尼介质对圆板运动时间和板中心点残余挠度的影响曲线。     

异型孔空心叶片壁厚检测的试验研究

发动机叶片的结构型式和制造误差，直接影响发动机的性能和使用寿命。运用超声波法和电涡流法，对两种不同材料和形式的试件进行了试验。电涡流法受到探头直径和试件几何尺寸的影响，测量误差大，超声波法由于存在测量盲区，测量厚度的下限受到限制。但测量值与实际值相关，若对探头加以改进，用于异型孔空心叶片壁厚检测是可行的。     

行星际空间MHD模拟激波跃变关系分析

分析了模拟得到的可以传播到1AU以远的日地空间磁流体力学激波与Rankine-Hugnoniot跃变关系的符合程度．通过对模拟激波的结构及其在传播过程中的演化进行的分析，提出了模拟激波的定位方法；基于所提出的定位方法，利用向长青提出的确定MHD激波局地参数的方法计算了模拟得到的激波与Rankine-Hugnoniot跃变关系的偏差．结果表明在激波传播到100Rs以后，激波对中前向快激波与Rankine-Hugnoniot关系的符合达到很高的程度，相对误差在10^-2数量级以内；并且在激波传播到150 Rs以后，相对误差在10^-3数量级以内．这个结果说明文中所使用的有限差分数值格式能较好地模拟激波．     

后向台阶层流分离剪切层特性研究

应用激光测速仪对生向台阶层流边界层分离产生的剪切层在再附前的发展进行了测量，得到了时均速度、湍流强度及剪切层厚度等的分布特性，并研究了来流湍流度对台阶后流场湍强度分布及剪切层发展的影响，实验中发现台阶后有一个流速降低的区域，对此从涡动力学的角度作了解释。     

飞机壁板结构的声疲劳计算及试验

 <正> 飞机结构所承受的噪声载荷声压级超过130dB时,经较长时间激励,往往在噪声诱导应力较大的区域里产生疲劳破坏。而在各种类型的结构件中声疲劳破坏的相对发生率以蒙皮壁板结构为最高。 本文采用矩形铝合金平板来模拟蒙皮壁板结构,对其进行了声疲劳寿命计算与试验研究.     

Transonic buffet control research with two types of shock control bump based on RAE2822 airfoil

Current research shows that the traditional shock control bump (SCB) can weaken the intensity of shock and better the transonic buffet performance.The author finds that when SCB is placed downstream of the shock,it can decrease the adverse pressure gradient.This may prevent the shock foot separation bubble to merge with the trailing edge separation and finally improve the buffet performance.Based on RAE2822 airfoil,two types of SCB are designed according to the two different mechanisms.By using Reynolds-averaged Navier-Stokes (RANS) and unsteady Reynolds-averaged Navier-Stokes (URANS) methods to analyze the properties of RAE2822 airfoil with and without SCB,the results show that the downstream SCB can better the buffet performance under a wide range of freestream Mach number and the steady aerodynamics characteristic is similar to that of RAE2822 airfoil.The traditional SCB can only weaken the intensity of the shock under the design condition.Under the off-design conditions,the SCB does not do much to or even worsen the buffet performance.Indeed,the use of backward bump can flatten the leeward side of the airfoil,and this is similar to the mechanism that supercritical airfoil can weaken the recompression of shock wave.     

Satellite launch vehicle effect on the Earth’s lower ionosphere: A case study

The effect of the rocket exhaust products on the D-region of the ionosphere is investigated with the help of Very low frequency (VLF) electromagnetic wave propagation characteristics within the Earth-ionosphere waveguide. The changes in the electron density profile are computed from the observed VLF signal amplitude perturbations about 3 dB during the rocket launch. We find a localized electron depletion in the lower ionosphere at an altitude of around 58 km, that is thought to be originated by the attachment of ionospheric ion and molecular hydrogen along with water molecule in the exhaust product of first stage burn of Geosynchronous Launch Vehicle (GSLV) rocket at the time of GSLV launched from Sriharikota, India, on 27 August 2015 at 11:22 UT (16:52 IST). The ionospheric depletion perturbed the navigational VLF signal (VTX = 17 kHz) 134 s after the launch of the GSLV rocket.